Process for making sutures



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of one form of apparatus for performing the steps of the second chemicaltreatment and winding on drying racks shown in FIG. 1.

FIG. 8 is a diagrammatic ventical, longitudinal section of analternative continuous form of drying apparatus and FIG. 9 is adiagrammatic horizontal, longitudinal section of the drying apparatusshown in FIG. 8.

Before describing the invention in detail it is to be understood thatvthe description and terminology used therein are `for the purpose ofillustration only and do not constitute any limitation o-f theinvention.

As starting material we may use any known or suitable ribbon or strip ofanimal gut for example the sub-mucosa layer of the small intestine ofsheep.

Referring to FIG. 6, two strips of gut 12 and 14 are positively yjoinedend to end to for-m a continuous strip 16. We prefer to join the stripby knotting, for example with -a pair of loop knots or binder knotscomposed of two single loop knots 18 and 20. The loop knot is preferredbecause it can be easily tied with wet, slippery gut and a pair of loopknots holds the pieces securely. Other knots can be used such as asquare knot, but, as far as our investigation has gone, we havefound itnecessary that two knots be used. Regardless of the type of knot whichis used we have found that tension on .the strip 16 when the gut is Wetcauses a single knot 18 to slipalong The second knot 20 stops thisslipping and a very slight amount of tension on the strip I16 combines`the two knots into a small tight lump 21 (FIG. 2) in which theindividual knots are not distinguishable. A square knot slips in similarmanner unlessit -is given an extra tie or knot ove-r the square.Surprisingly the lump formed by the knot is so small and compact that it`does not interfere with the passing of the strip through guides,between feed rollers or through the yer of a spinning machine.

One example of a process or series of processes to which our inventionis applicable is illustrated by the flow diagram in FIG. l. After thestrips have been joined as shown in FIG. 6, the continuous strip may bedrawn through a rst chemical ytreating bath which may perform any of avariety of known chemical treatments for producing gut having desiredphysical and chemical characteristics. One example is to chromicize ortan the gut to provide the necessary or desired delay in absorption byhuman tissues. Thereafter the gut, whether a single strip, or a numberof parallel strips, is spun in-to string after which the spun or twistedstring may be given a second chemical treatment for example in a knownformaldehyde bath. After this the string is dried for example by windingit on d-rying racks, and placing the tracks lin drying ovens or bypassing the string continuously through a series of drying ovens.Thereafter the strand is cut to lengths suitable for use as individualsutures and the segments of the string containing the knots may bediscarded, or cut into shorter lengths free of knots.

Our invention is applicable to any of the known chemical processes fortreating and preparing animal gut to make sutures. While a tirstchemical treatment such as chrom-icizing and a second chemical treatmentsuch as tanning by Iformaldehyde have been given 'as examples it ispossible to canry out our invention yby using only one chemical eitherbefore or after spinning, as indicated by the `broken lines around thechemical steps in the ilow diagram of FIG. l.

Referring to FIG. 2, a single gut ribbon 16 is wound on -a spool 22splined on a shaft 24 driven by any suitable motor 26 which may be forexample, a constant speed motor o-r a constan-t torque motor. The spoolis partially immersed in water in order to preserve the desired watercontent of the gut. The strand 16 is preferably wound on the drum 22 byany suitable level Winder 28. 'Ihe spool is removed trom the water afterthe desired length of gut s wound on it, -and may be either transferredimmediately to the next step in the process, or may be sto-red in anatmosphere of the necessary temperature and humidity, for a substantialperiod of time, for example 12 to 24 hours.

The next step may be the first chemical treatment illustrated in FIG. 3.The spool is of novel construction and has novel `floatingcharacteristics making `it especially suitable for this process. Asshown in FIGS. 3 and 5 for example, the spool has a hollow cylinder 30on which the gut is wound, and a pair of end flanges 32 attached to itby a Water tight fastening, as by being integrally molded or secured byadhesive. The end flanges project radially beyond the coil of gut to belaid on the spool. Each end flange has a coaxial opening 34 to receive ashaft, as 24 in FIG. 2. At least one of the openings is non-circular,for example like a key hole, to -receive a spline on the shaft orotherwise form a drivin-g connection with the shaft. Preferably eachange has the same kind of hole. Whenever the spool is placed in a liquidbath, as in a container 36, the spool sinks until air trapped in thespool floats it. Liquid flows into the spool as long as air can escape,from it through one of the openings. When the liquid level inside thespool reaches the upper edge of the opening, the air vent is closed andno more water can ow in.

When this occurs the spool substantially floats in the bath. Ideally theweight of the spool and the gut on it is substantially equal to Itheweight of the liquid displaced so that the spool can be rotated withoutany Ifriction contactwith the sides or bottom of the container. However,if the spool is very slightly heavier than the liquid d-isplaced, theanges will rest very lightly against the bottom of the bath, or againstrods 38 placed in the bath. These will hold the spool so that when -itrotates under the unwinding action of the gut, as will be explained, therods hold the spool in proper position and constrain its rotation to besubstantially about its axis. Such resting on t-he bottom, or on therods should be as light as possible so that the apparent weight of thespool on them -is from zero to some very small positive value, justenough to keep the spool from wobbling. This is what we mean bysubstantially oating. This is achieved by proper selection of thedensity and amount of material in the spool, the location of the maximumradial distance of the edge of the hole 34 and the density of theliquid. The spool is intended to be rotated constantly, as will beexplained, and the end of the spline slot in the opening 34, when up,determines the amount of liquid that can enter the spool.

Ordinarily the weight of the spool is such that the weight of the gut,even in long lengths of hundreds or thousands of feet, can be neglected.

Referring to FIG. 3, a spool 22, made and proportioned as justdescribed, and wound with a strip of single layer gut ribbon 5000 feetlong, for example, is placed in a tank 36 in which water is kept at aconstant level by any known means. The ribbon 16 may be passed over oneor more guides 40, 42, under an entrance roller 44 into liquid in a tank46, under an exit rolle-r 48, over a guide 50 and onto a take-up spool52, Which may be made like spool 22, and is immersed in liquid in a tank54 and splined to a shaft 56 driven by a constant speed motor or aconstant torque motor such as 58. This unwinds the ribbon 16 from thespool 22 against the negligible resistance of the floating spoolrotating in the liquid, and draws the ribbon through the bath at thedesired speed to provide the desired exposure to the chemical treatmentin tank 46. The resistance to rotation offered by the spool determinesthe tension of the ribbon being unwound.

The liquid in tank 36 may be water or any desired chemical, to preservethe moist-ure content of the gut, to provide any desi-red chemicaltreatment, and to oat the spool. The liquid in the tank 46 may provideany known chemical treatment such as chromicizing or tanning. It isimportant that the tension required to unwind the ribbon from the spool22 be very low, for at this point the tensile strength of the ribbon isvery low. l

After being wound on the spool 52 (or on the spool 22 e) if chemicaltreatment A is omitted), a string is spun from one or more ribbons 16,for example by the alternative processes shown in FIGS. 4 and S.

Referring to FIG. 5, aspool 22 or 52, holding a singlelayer of untreatedor chemically treated gut, is driven by a constant speed motor 60, tounwind at zero tension a ribbon 16 which then passes over guide 62 to aspinning apparatus generally designated by 64. This may be ofconventional form but we prefer to use a flyer including an inverted cup66, rotated in suitable bearings, not shown, by any suitable motor, notshown, and carrying within it a flyer tube including a central enteringtube 68 and symmetrically disposed flyer tubes 69 and 70. Each flyerItube terminates in a trailing portion 72 which delivers the twistedstring tangentially to a spool or drum 74 -on which it 'forms thepackage 76. Only one flyer tube'69 br 70 is used. Two are provided tofacilitate threading and to achieve balance. The spool 74 is mounted ona shaft 78 which is freely rotatable in bearings not shown against `theresistance of any suitable eddy current drag brake 80. The brake, shaftand spool are cyclically traversed vertically, as is known, by anysuitable means. The speed of the motor 60 is synchronized with the speedof the flyer so that the linear speed of unwinding the ribbon from thespool 22 or 60 equals the linear speed of laying the string on thepackage.

A feature of our invention is the spraying of the package duringspinning by a liquid which at least preserves or restores the moisturecontent of the gut and preferably treats the gut chemically at the sametime. The twisting tends to express water from the gut and thecentrifugal action of the flyer tends to throw off still more. Tocounteract these tendencies we enclose the spinning apparatus in acontainer 82 and continuously spray the package with suitable liquidfrom a spray head 84.

IIf chemical treatment is not desired the package may be sprayed withwater, just to restore and preserve the moisture content of the gut.However our invention includes spraying with any desired chemicaltreating solution, which Vmay take the place of chemical treatment B inFIG. 1. For example the package may be sprayed with a humectant such asglycerine. The strength of the solution is selected to produce thedesired characteristics in the gut during the time the gut is exposed tothe remainder `of the process before drying.

Alternatively the gut may be spun as shown in FIG. 4. One or moreribbons 16, on spools 22' or 52 may be floated in one or more tanks S4each of which is precisely like tank 36 in FIG. 3 and contains water forfloating the spools and preserving the water content of the gut. One ormore strands may be passed over a guide 86 and fed between positivelydriven feed rollers 88 to the spinning device 64 which operates likethat shown in FIG. 5. The floating spools provide the minimum resistanceto rotation and thus develop the minimum tension in the ribbons 16between the spools and the feed rolls. The feed rolls being verticallyabove the yer intake tube 68 deliver the ribbons at no tension exceptthat inherently developed by the spinning operation.

Where a plurality of ribbons 16 are spun, as in FIG. 6, preferably theribbons are laid flat in a vertical stack in the guide 86 and so arepressed together flat by Ithe feed rolls before being spun.

After spinning, and especially if the package is sprayed with wateronly, the twisted string may be put through chemical treatment B, whichmay consist of further tanning or hardening, as by a formaldehydesolution. This is shown in FIG. 7.

The spool 74 holding the string 89 twisted by the spinning operation issplined to a shaft 90 which may be immersed in water in a tank 92 andconnected to a drag brake, 'such as an eddy current brake 94. The string89 is pulled over suitable guides and under the rollers 96 immersed insuitable treating liquid in a tank 100 by a flat rectangular dryingframe 102 rotated by a motor 164. Preferably the string is led over alevel Winder 166 which winds the string in separated lturns about thedrying frame. The drag brake develops the desired tension in the tank16d for the chemical treatment, and the speed of winding, length of tankand strength of the soluvtion are related to provide the desired time oftreatment. If the chemical treatment B is omitted, the string is wounddirectly von the frame from the spool 74. This may be done, fo-r examplewhen the package in thee spinning operation is sprayed with the chemicaltreating solution.

When the frame is filled the string is severed, the frame is hung in anysuitable drying roorn or oven until the string is dry. Then all theloops or turns of string are pushed over to one side of the frame andsevered at both ends of the frame so that each loop or turn provides twostrings, each the length of the frame, for example 60 inches. Thoselengths containing no fastenings `or knots are then selected forsutures. Also each length which contains a knot only near its end can beused for shorter sutures such as 4() inches. In some instances suturesas short as 30 inches may be used, in which case lengths having knotsnear the center may be selected for sutures. Thus the invention providesa continuous string which can be conveniently processed and cut up intoindividual sutures with an extremely small amount of waste.

Instead of drying the string on racks or frames as shown in FIG. 7 wemay dry continuously indefinite lengths of string as shown in FIGS. 8and 9. Twisted and finished, but wet, string 89 may be led either fromthe spool 74 or from the tank 10i) continuously through a series ofdrying chambers 108, and 112. In each chamber the string may pass overfour rollers 114 in a continuous and progressive coil. The rolls in eachchamber may be positively driven by a chain and sprocket drive 116actuated by a motor 113. One or more of the rolls may be driven and theremainder of the rolls may form anti-friction supports for the string.The rolls may be skewed or inclined as known inl the synthetic filamentart to cause the string to progress along the rolls in a series ofseparated turns. The rolls may be supported at one end only, as known inthe synthetic filament art, to facilitate initial threading of thestring around the rolls.

The atmosphere in the separate drying chambers may be, of course,controlled as desired. For example the humidity of the chambers maydecrease progressively from 108 to 110` to ll2 while the temperature inall ovens may remain the sarne, or may increase progressively from 108to 110 to 112. The length of the pass through each oven is related tothe temperature and humidity to expose the string for the desired lengthof time to accomplish the necessary drying.

Variations of the invention may be made within the scope of the appendedclaims. For example the spools from which the ribbon is unwound atvarious steps in the process may be entirely and freely floating. Wehave described a spool in which the weight of the spool, gut, liquid andentrapped air is exactly equal to, or very slightly greater than, theweight of liquid displaced. If the Weight of the spool is slightlygreater than `the Weight of liquid displaced, the spool will rest on thebottom of the tank or on the rods 38. If the weight becomes exactlyequal to the Weight of liquid displaced, the spool will stop sinkingbefore it engages the bottom, and will float freely. In such case thefront and back walls of the tank can be placed to act as guides toprevent wobbling in unwinding and the same low friction characteristicswill prevail. It is also possible to place the rods 33 above the spooland adjust the liquid level in the tank and the amount of air trapped inthe spool so that the weight of liquid displaced by the spool isslightly greater than the weight of the spool. In this case the spoolwill be yieldingly held up against the rods, or float up against them.All of the variations described in this paragraph come Within themeaning of substantially oating, as used in the following claims.

We claim:

1. In a method of making continuous strings of animal gut theimprovement which includes positively joining together end-to-end aseries of ribbons of wet animal gut to form a continuous ribbon,continuously and progressively twisting the ribbon into a string whilewetting the gut with liquid, and passing the string continuously througha drying atmosphere.

2. In a method of making continuous strings of animal gut theimprovement which includes positively joining together end-to-end aseries of ribbons of wet animal gut to form a continuous ribbon,continuously and progressively twisting the ribbon into a string whilewetting the gut with liquid, and passing the string continuously over aseries of rollers in a drying atmosphere.

3. In a method of makin-g continuous strings of animal gut theimprovement which includes positively joining together end-to-end aseries of ribbons of wet animal gut to form a continuous ribbon,continuously and progressively twisting the ribbon into a string whilewetting the gut with liquid, and passing the string continuously over aseries of positively driven rollers in a drying atmosphere.

4. In a method of making continuous strings of animal gut `theimprovement which includes positively joining together end-to-end aseries of ribbons of Wet animal gut to form a continuous ribbon,twisting the ribbon into a string while spraying the gut with liquid,and passing the string continuously through a series of dryingatmospheres of progressively decreasing humidity and progressivelyincreasing temperature.

References Cited by the Examiner UNITED STATES PATENTS4 '1,006,85410/1911 Kuhn 57-35 X 2,391,483 12/1945 Selby 57-164 2,558,734 7/1951Creswell 68--181 2,627,103 2/ 1953 Jennings 28-76 l FOREIGN PATENTS310,884 2/ 1930 Great Britain.

MERVIN STEIN, Primary Examiner.

1. IN A METHOD OF MAKING CONTINUOUS STRINGS OF ANIMAL GUT THEIMPROVEMENT WHICH INCLUDES POSITIVELY JOINING TOGETHER END-TO-END ASERIES OF RIBBON OF WET ANIMAL GUT TO FORM A CONTINUOUS RIBBON,CONTINUOUSLY AND PROGRESSIVELY TWISTING THE RIBBONINTO A STRING WHILEWETTING THE GUT WITH LIQUID, AND PASSING THE STRING CONTINUOUSLY THROUGHA DRYING ATMOSPHERE.